Web design and arrangement for reducing a radial distribution fault in a wound heat exchanger

ABSTRACT

The invention relates to a heat exchanger (1) for the indirect transfer of heat between a first and at least one second medium (M, M′), having a jacket space (I) for receiving the first medium (M), a core pipe (20) arranged in the jacket space (I), a pipe bundle (15) arranged in the jacket space (I), which bundle comprises a plurality of pipes (10) which are each wound around the core pipe (20) such that the pipe bundle (15) has a plurality of pipe layers arranged on top of each other (100, 101, 102, 103) which each comprise at least one pipe (10), a pipe bundle gap (200, 201, 202, 203) being present between all the adjacent pipe layers (100, 101; 101, 102; . . . ) and a plurality of spacers (30) being arranged in each pipe bundle gap (200, 201, 202, 203) to support the pipe layers (100, 101, 102, 103). According to the invention, the spacers (30) each have a thickness (D) in the radial direction (R) of the pipe bundle (15), the thicknesses (D) of the spacers (30) of a first pipe bundle gap (200) each being greater than the thicknesses (D) of the spacers of a second pipe bundle gap (203), which lies further to the outside in the radial direction (R) of the pipe bundle (15) than the first pipe bundle gap (200).

The invention relates to a heat exchanger for indirect heat transferbetween a fluid first medium and at least one fluid second medium.

Such a heat exchanger is used, for example, in natural gas liquefactionplants and has a shell space for receiving a first medium (refrigerant)and a plurality of tubes arranged in the shell space for receiving atleast one second medium, which are wound around a core tube and form atube bundle having a plurality of tube layers lying one above the other.Furthermore, the tube bundle has a plurality of spacers for supportingor mechanically stabilizing the tube layers, each of which is arrangedin a tube bundle gap between two adjacent tube layers or in particularalso in an innermost tube bundle gap between an innermost tube layer andan outer side of the core tube.

In this case, the number of spacers per tube bundle gap is generallyconstant so that the spacers for supporting the tube layers can bearranged one above the other in the radial direction of the tube bundle.In this way, the weight of all tube layers can be supported via thespacers without damaging the tubes of individual tube layers.

However, in a cross-sectional plane of the shell space perpendicular tothe longitudinal axis (vertical) of the core tube or tube bundle, thespacers in each case reduce the free cross-sectional area of the shellspace between the tube layers so that, due to the constant number ofspacers per tube bundle gap (see above), the free cross-sectional areasbetween the inner tube layers or in the inner tube bundle gaps undergo agreater relative reduction than the free cross-sectional areas of thetube bundle gaps located further to the outside. As a result, thecalculated pressure drop in the shell space would not be constant in theradial direction, but rather would be greater on the inside than furtheroutside. However, since the flow through the gaps arises in reality insuch a way that the same pressure loss prevails everywhere, a higherflow velocity results for the gaps lying further to the outside than forthe gaps lying further to the inside, and therefore a higher dynamic andlower static pressure component. In the shell space, this can then leadto an incorrect distribution of the phase of the first medium guided inthe shell space in the direction of the outer layers of the tube bundle.

Proceeding therefrom, the present invention is therefore based on theproblem of creating a heat exchanger of the type mentioned at the outsetwhich counteracts the aforementioned maldistribution.

This problem is solved by a heat exchanger having the features of claim1, wherein advantageous embodiments of the invention are specified inthe dependent claims and described below.

According to claim 1, it is provided that the spacers each have athickness in the radial direction of the tube bundle, wherein thethicknesses of the spacers of a first tube bundle gap are in each casegreater than the thicknesses of the spacers of a second tube bundle gaplocated further outward in the radial direction of the tube bundle,i.e., closer to the shell than is the first tube bundle gap.

In particular, a constant hydraulic diameter of the free flowcross-sections in the tube bundle gaps (between the tube layers and thespacers) can thereby be made possible or adjusted by reducing the radialthickness of the spacers in the radial direction from the core tubetoward the shell.

The individual tubes are preferably wound helically onto or around thecore tube 4. The tube bundle gap is in each case correspondinglydesigned in particular in the form of an annular gap.

It is preferably provided that the core tube extends along alongitudinal axis of the shell, wherein the longitudinal axis isvertically aligned when the heat exchanger is arranged as intended orready for operation.

Furthermore, according to one embodiment of the invention, it isprovided that the thicknesses of those spacers arranged in the same tubebundle gap are the same.

Furthermore, one embodiment of the invention provides that the spacershave more than two, in particular three to four, different thicknessesin the radial direction of the tube bundle, wherein the thickness of thespacers decreases or remains the same in the radial direction from thecore tube to the shell from tube bundle gap to tube bundle gap. That is,in particular, in each case two or more tube bundle gaps adjacent toeach other in the radial direction may have spacers of the samethickness, and only thereafter a decrease in thickness takes place (atthe transition to the next tube bundle gap located further outward).That is, the thickness does not necessarily have to decrease from tubebundle gap to tube bundle gap but may also decrease outwardly in astepwise manner.

Furthermore, according to one embodiment of the invention, it isprovided that the thickness of the spacers decreases in the radialdirection from the core tube to the shell from tube bundle gap to tubebundle gap. Here, the thickness of the spacers towards the outside (inthe radial direction) thus decreases strictly monotonically.

Furthermore, one embodiment of the invention provides that the spacersare designed as longitudinally extending webs, each extending in alongitudinal direction. The spacers or webs can have a rectangularcross-section perpendicular to the longitudinal direction, which hassaid thickness, and a width perpendicular thereto (in thecircumferential direction of the tube bundle).

Furthermore, one embodiment of the invention provides that thelongitudinal direction of the respective spacer runs parallel to thecore tube or to the longitudinal axis of the shell/core tube.

Furthermore, according to one embodiment of the invention, it isprovided that the respective spacer extends along the core tube or thelongitudinal axis over an entire length of the tube bundle.

Furthermore, it is provided according to one embodiment of the inventionthat the spacers are arranged equidistantly relative to one another inthe circumferential direction of the tube bundle in the respective tubebundle gap.

Furthermore, according to one embodiment of the invention, it isprovided that the spacers are grouped in such a way that a plurality ofspacers for supporting the tube layers are arranged one above the otherin a radial direction of the tube bundle.

Furthermore, one embodiment of the invention provides that the number ofspacers in the each tube bundle gap is the same.

Further features, advantages and embodiments of the invention will beexplained below with reference to the figures.

The figures show:

FIG. 1 a partial sectional view of an embodiment of a heat exchangerwith spacers of a tube bundle of the heat exchanger that have decreasingthicknesses in the radial direction; and

FIG. 2 a schematic sectional view of a tube bundle of a heat exchangeraccording to the invention along a sectional plane which runsperpendicular to the longitudinal axis of the core tube according toFIG. 1.

FIG. 1 shows an embodiment of a heat exchanger 1 according to theinvention. This has a shell 2, which encloses a shell space I of theheat exchanger 1. Arranged in the shell space I is a tube bundle 15supplied with a fluid phase of a first medium M, which is, for example,a refrigerant, along the longitudinal axis Z of the heat exchanger 1 orshell 2. At least one second fluid medium M′ is conducted in the tubes10 of the tube bundle 15 so that it can enter into an indirect heatexchange with the first medium M that is conducted in the shell space I.Connecting pieces 3, 4 can be provided in the shell 2 for introducingthe first medium M into the shell space I, or for removing the firstmedium M from the shell space I.

The tube bundle 15 has a plurality of tubes 10, wherein the tubes 10 areeach wound around or onto a core tube 20 arranged in the shell space I,at least sectionally like a helical line, said core tube extending alongthe longitudinal axis Z so that a plurality of tube layers 101, 102,103, 104 are formed which lie one above the other in the radialdirection R of the tube bundle 15 or of the core tube 20. The radialdirection R is in each case orthogonal to the longitudinal axis Z andpoints outwardly from the longitudinal axis Z toward the shell 2. Inorder to admit at least one second medium M′ into the tube bundle 15,the tubes 10 are in fluidic connection with at least one connectingpiece 5 provided on the shell 2. Furthermore, at least one connectingpiece 6 is provided on the shell 2 to withdraw the at least one mediumM′ from the tube bundle 15. In order to introduce different second mediaM′, the tube bundle 15 can also be divided into tube groups, each ofwhich is assigned an inlet or connecting piece 5 and an outlet orconnecting piece 6. FIG. 1 shows three such tube groups by way ofexample.

Furthermore, the tube bundle 15 can be surrounded by a cylindrical skirt7 in order to suppress a bypass flow past the tube bundle 15.

For mechanically stabilizing the tube bundle 15 or the individual tubelayers 100, 101, 102, 103, several spacers 30 are provided (see inparticular FIG. 2), each arranged in a tube bundle gap 200, 201, 202,203, wherein the respective tube bundle gap 200, 201, 202, 203 is formedby two adjacent tube layers 100, 101; 101, 102, . . . which lie oneabove the other in the radial direction R, wherein the innermost tubebundle gap 200 lies between an outer side 20 a of the core tube 20 andthe innermost tube layer 100.

The spacers 30 can support the weight of the individual tube layers 100,101, 102, 103 via the spacers 30. A constant number of spacers 30 aretherefore preferably provided in each tube bundle gap 200, 201, 202, 203so that the spacers 30 can be arranged one above the other in the radialdirection R.

In the prior art, however, said constant number of spacers 30 per tubebundle gap 200, 201, 202, 203 causes the relative reduction of a freecross-sectional area F, that is oriented transversely to thelongitudinal axis Z, of the respective tube bundle gap 200, 201, 202,203 due to the spacers 30 arranged one above the other in the radialdirection R to be larger closer to the core tube 20 than in the case oftube bundle gaps located further outwardly. Close to the core tube 20,this leads to a greater pressure drop on the shell space side in thetube bundle 15 than in the case of regions or tube bundle gaps locatedfurther to the outside in the radial direction R.

In order to be able to influence or compensate for this pressure drop ina controlled manner, it is provided according to the invention (see FIG.2) that the spacers 30 each have a thickness D in the radial direction Rof the tube bundle 15, wherein the thicknesses D of the spacers of afirst tube bundle gap (e.g. 200) are each greater than the thicknessesof the spacers of a second tube bundle gap (e.g., 201) lying furtheroutward in the radial direction R of the tube bundle 15, i.e., lyingcloser to the shell 2 than the first tube bundle gap (e.g., 200). Thethicknesses of the spacers 30 are preferably of equal size within a tubebundle gap 200, 201, 202, 203.

According to one embodiment, it can be provided that the spacers 30 havemore than two, in particular three to four, different thicknesses D inthe radial direction R of the tube bundle 15, wherein the thickness D ofthe spacers 30 decreases or remains the same in the radial direction Rfrom the core tube 20 toward the shell 2 from tube bundle gap to tubebundle gap. That is, in particular, in each case two or more tube bundlegaps adjacent to each other in the radial direction R can have spacers30 of the same thickness, and only thereafter is there a decrease in thethickness D so that there will be a stepwise decrease in the thicknessesD to the outside. Alternatively, it can be provided according to FIG. 2that the thickness D of the spacers 30 decreases in the radial directionfrom the core tube 20 to the shell 2 from tube bundle gap to tube bundlegap 200, 201; 201, 202; 202, 203.

The spacers 30 preferably take the form of longitudinally extending webs30 (see FIG. 1), each extending in a longitudinal direction. The spacers30 or webs can have a rectangular cross-section perpendicular to thelongitudinal direction. It is preferably provided that the longitudinaldirection of the respective spacer runs parallel to the core tube 20 orparallel to the longitudinal axis Z. Furthermore, it is preferablyprovided that the respective spacer 30 extends along the core tube 20over an entire length of the tube bundle 15.

In the circumferential direction U of the tube bundle 15, the spacers 30are arranged in the respective tube bundle gap 200, 201, 202, 203preferably equidistantly to one another.

Due to the reduction of the thicknesses D of the spacers 30 in theradial direction R of the tube bundle, the free cross-sectional area Fof the further outer tube bundle gaps (e.g., 202, 203) can be reduced orcan be matched to the free cross-sectional areas F of the tube bundlegaps (e.g., 200, 201) lying more inwardly, which counteracts theshell-side maldistribution of the first medium or of the refrigerant.

List of reference signs 1 Wound heat exchanger 2 Shell 3 Connectingpiece (inlet) 4 Connecting piece (outlet) 5 Connecting piece (inlet) 6Connecting piece (outlet) 7 Skirt 10 Tubes 15 Tube bundle 20 Core tube20a Core tube outer side 30 Spacer 100, 101, 102, 103 Tube layers 200,201, 202, 203 Tube bundle gap D Thickness I Shell space F Freecross-sectional area M First medium M′ Second medium R Radial directionU Circumferential direction Z Longitudinal axis (vertical)

1.-12. (canceled)
 13. A heat exchanger for indirect heat transfer between a first and at least one second medium, having a shell space for receiving the first medium, a core tube arranged in the shell space, a tube bundle arranged in the shell space that has multiple tubes, each of which is wound around the core tube so that the tube bundle has multiple tube layers which are arranged one above the other and each of which has at least one tube, wherein there is a tube bundle gap between every two adjacent tube layers, wherein several spacers for supporting the tube layers are arranged in each tube bundle gap, wherein, the spacers each have a thickness in the radial direction of the tube bundle, wherein the thicknesses of the spacers of a first tube bundle gap are in each case greater than the thicknesses of the spacers of a second tube bundle gap located further outward in the radial direction of the tube bundle than the first tube bundle gap.
 14. The heat exchanger according to claim 13, wherein the thicknesses of the spacers which are arranged in the same tube bundle gap are the same.
 15. The heat exchanger according to claim 13, wherein the spacers have more than two, in particular three to four, different thicknesses, wherein the thickness of the spacers decreases or remains the same in the radial direction from the core tube to the shell from tube bundle gap to the tube bundle gap.
 16. The heat exchanger according to claim 13, wherein the thickness of the spacers decreases in the radial direction from the core tube to the shell from tube bundle gap to tube bundle gap.
 17. The heat exchanger according to claim 13, wherein the spacers are designed as longitudinally extending webs, each of which extends in a longitudinal direction.
 18. The heat exchanger according to claim 17, wherein the longitudinal direction of the respective spacer runs parallel to the core tube.
 19. The heat exchanger according to claim 13, wherein the respective spacer extends along the core tube, at least over an entire length of the tube bundle.
 20. The heat exchanger according to claim 13, wherein the spacers are arranged equidistantly to one another in the respective tube bundle gap in the circumferential direction of the tube bundle.
 21. The heat exchanger according to claim 13, wherein between an innermost tube layer in the radial direction of the tube bundle and an outer side of the core tube, there is an innermost tube bundle gap in which a plurality of spacers are arranged.
 22. The heat exchanger according to claim 13, wherein the spacers are grouped in such a way that a plurality of spacers for supporting the tube layers are arranged one above the other in a radial direction of the tube bundle.
 23. The heat exchanger according to claim 13, wherein the number of spacers in the respective tube bundle gap is the same.
 24. The heat exchanger according to claim 13, wherein the number of spacers differs in at least two tube bundle gaps. 